Nucleation and Growth of μc-Si:H n- and p-Type Layers in a-Si:H p-i-n AND n-i-p Solar Cells: Real Time Spectroellpsometry Studies

1996 ◽  
Vol 452 ◽  
Author(s):  
Joohyun Koh ◽  
H. Fujiwara ◽  
C. R. Wronskii ◽  
R. W. Collins
Keyword(s):  
Optical Properties ◽  
Solar Cells ◽  
Real Time ◽  
Size Effects ◽  
Growth Process ◽  
Nucleation And Growth ◽  
Microcrystalline Silicon ◽  
Analysis Problem ◽  
Near Surface ◽  
P Type

AbstractWe have applied real time spectroellipsometry (RTSE) to study the growth of microcrystalline silicon n- and p-layers [μc-Si:H:(P,B)] incorporated into amorphous silicon (a-Si:H) p-i-n and n-i-p solar cells, respectively. In previous research, we have applied RTSE to characterize a-Si:H solar cells having only amorphous component layers. The μc-Si:H(P,B) component layers, however, pose a more difficult RTSE analysis problem for two reasons. First, the near-surface of the underlying i-layer is modified in the μc-Si:H:(P,B) growth process, and second, the microstructural evolution near the i/(n,p) interfaces is very complicated. From RTSE spectra (1.5 < hv < 4 eV) collected every ∼4–15 s during growth, we have extracted the time evolution of the μc-Si:H:(P,B) layer microstructure, thicknesses, and optical properties along with the modifications that the near-surface i-layer properties undergo in the formation of the i/(n,p) interfaces. We suggest that the beneficial optical properties of the microcrystalline layers may be due to size effects in the crystallites that make up the films.

DEVELOPMENT OF HIGHLY CONDUCTIVE BORON-DOPED MICROCRYSTALLINE SILICON FILMS FOR APPLICATION IN SOLAR CELLS

2006 ◽  
Vol 20 (03) ◽  
pp. 303-314 ◽  
Author(s):  
QING-SONG LEI ◽  
ZHI-MENG WU ◽  
JIAN-PING XI ◽  
XIN-HUA GENG ◽  
YING ZHAO ◽  
...  
Keyword(s):  
Solar Cells ◽  
Substrate Temperature ◽  
Chemical Vapor ◽  
Dark Conductivity ◽  
Silicon Films ◽  
Microcrystalline Silicon ◽  
Very High Frequency ◽  
Boron Doped ◽  
Deposition Processes ◽  
P Type

We have examined the deposition of highly conductive boron-doped microcrystalline silicon (μc- Si:H ) films for application in solar cells. Depositions were conducted in a very high frequency plasma enhanced chemical vapor deposition (VHF PECVD) chamber. In the deposition processes, various substrate temperatures (TS) were applied. Highly conductive p-type microcrystalline silicon films were obtained at substrate temperature lower than 210°C. The factors that affect the conductivity of the films were investigated. Results suggest that the dark conductivity, which was determined by the Hall mobility and carrier concentration, is influenced by the structure. The properties of the films are strongly dependent on the substrate temperature. With TS increasing, the dark conductivity (σd) increases initially; reach the maximum values at certain TS and then decrease. Also, we applied the boron-doped μc- Si:H as p-layers to the solar cells. An efficiency of about 8.5% for a solar cell with μc- Si:H p-layer was obtained.

A Simple Optical Properties Modeling of Microcrystalline Silicon by the Effective Medium Approximation Method

1996 ◽  
Vol 426 ◽  
Author(s):  
Woo Yeong Cho ◽  
Koeng Su Lim ◽  
Hyun-Mo Cho
Keyword(s):  
Optical Properties ◽  
Approximation Method ◽  
Volume Fraction ◽  
Crystalline Silicon ◽  
Solar Spectrum ◽  
Effective Medium ◽  
Effective Medium Approximation ◽  
Microcrystalline Silicon ◽  
Two Phase ◽  
P Type

AbstractThe optical properties of microcrystalline silicon (µc-Si) were estimated using the EMA (Effective Medium Approximation) method. This modeling was based on two-phase mixture, amorphous silicon (a-Si) and crystalline silicon (c-Si) with volume fractions of fa and fc respectively. From this modeling, it could be possible to understand thatµc-Si has lower light absorption characteristics than a-Si over all solar spectrum by considering hydrogen involvement in embedded a-Si part of iic-Si and crystalline volume fraction. Also, it is proposed that p-type pe- Si is superior to n-type tic-Si because of its high optical gap of Eo4 and its low absorption coefficient spectrum shape.

Effect of c-Si1-xGex Thickness Grown by LPCVD on the Performance of Thin-Film a-Si/c-Si1-xGex/c-Si Heterojunction Solar Cells

2012 ◽  
Vol 1447 ◽  
Author(s):  
Sabina Abdul Hadi ◽  
Pouya Hashemi ◽  
Nicole DiLello ◽  
Ammar Nayfeh ◽  
Judy L. Hoyt
Keyword(s):  
Thin Film ◽  
Solar Cells ◽  
Layer Thickness ◽  
Surface Region ◽  
Absorber Layer ◽  
Buffer Layers ◽  
Optical Carrier ◽  
Near Surface ◽  
Heterojunction Solar Cells ◽  
P Type

ABSTRACTIn this paper the effect of Si1-xGex absorber layer thickness on thin film a-Si:H/crystalline-Si1-xGex/c-Si heterojunction solar cells (HIT cells) is studied by simulation and experiment. Cells with 1, 2 and 4 μm-thick epitaxial cap layers of p-type Si0.59Ge0.41 on top of 5 μm Si1-xGex graded buffer layers are fabricated and compared to study the effect of the absorber layer thickness. The results show no change in Voc (0.41V) and that Jsc increases from 17.2 to 18.1 mA/cm2 when the Si0.59Ge0.41 absorber layer thickness is increased from 1 to 4 μm. The effect of thickness on Jsc is also observed for 2 and 4 μm-thick Si and Si0.75Ge0.25 absorber layers. Experiments and simulations show that larger Ge fractions result in a higher magnitude and smaller thickness dependence of Jsc, due to the larger absorption coefficient that increases optical carrier generation in the near surface region for larger Ge contents.

Band Discontinuity Effect on a-Si:H and a-SiGe:H Solar Cells

1995 ◽  
Vol 377 ◽  
Author(s):  
X. Xu ◽  
A. Banerjee ◽  
J. Yang ◽  
S. Guha ◽  
K. Vasanth ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Solar Cells ◽  
Solar Cell ◽  
Valence Band ◽  
Cell Performance ◽  
Experimental Results ◽  
Microcrystalline Silicon ◽  
Solar Cell Performance ◽  
Single Junction ◽  
P Type

ABSTRACTThe electrical bandgap of microcrystalline silicon (μc-Si:H) p type layers used in a-Si:H alloy solar cells and the band edge discontinuities between μc-Si:H and a-Si:H alloys have been determined by internal photoemission measurements. The bandgap of μc-Si:H is found to be in the range of 1.50 to 1.57 eV, and the discontinuities at the conduction and the valence band edges are 0 to 0.07 and 0.26 to 0.35 eV, respectively. Use of these parameters in the numerical simulation of single-junction a-Si:H and a-SiGe:H alloy solar cells is found to predict experimental results of solar cell performance.

Structural and Optical Properties of a-Si:H/μc-Si:H:B Junctions in the a-Si:H-Based n-i-P Solar Cell Configuration

1997 ◽  
Vol 467 ◽  
Author(s):  
Joohyun Kohi ◽  
H. Fujiwara ◽  
C. R. Wronski ◽  
R. W. Collins
Keyword(s):  
Optical Properties ◽  
Solar Cell ◽  
Single Phase ◽  
Cell Structure ◽  
Chemical Vapor ◽  
Average Crystallite Size ◽  
Microcrystalline Silicon ◽  
Solar Cell Structure ◽  
P Type ◽  
Hydrogenated Amorphous

ABSTRACTWe have extended previous real time spectroscopie ellipsometry (RTSE) capabilities in order to investigate the effects of H2-plasma treatment of i-type hydrogenated amorphous silicon (a-Si:H) on the deposition of the overlying p-type microcrystalline silicon (μc-Si:H:B)) in the formation of an n-i-p solar cell structure. In this study, we compare in detail the nucleation and growth of p-layers by plasma-enhanced chemical vapor deposition (PECVD) from SiH4 highly diluted in H2 on the surfaces of untreated and H2-plasma treated a-Si:H i-layers. We find that for intended single-phase μc-Si:H:B p-layer PECVD under optimum conditions on an untreated i-layer surface, a wide gap (∼2.0 eV Taue gap) amorphous layer nucleates and grows in the first ∼150 Å. This layer develops uniformly to a bulk thickness of ∼150 Å, but gradually acquires a crystalline structure for thicknesses greater than the desired p-layer thickness (200 Å). In contrast, for p-layer PECVD under identical conditions on the H2-plasma treated i-layer, high-density crystalline nuclei form immediately. This conclusion is drawn on the basis of the unique optical properties of the bulk p-layer that develops on the surface of the H2-plasma treated i-layer. Specifically, an absorption onset near ∼2.5 eV is observed for a 48 Å fully-coalesced p-layer, as measured by RTSE at 200°C. For this μc-Si:H:B p-layer, the optical gap decreases by ∼0.15 eV with increasing thickness from 50 to 200 Å. This effect is attributed to a reduction in the quantum confinement energy with an increase in the average crystallite size in the film.

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